Parathyroid hormone secretion in normal man and in primary hyperparathyroidism: role of histamine H2 receptors.

The effect of histamine and histamine H2 receptors on secretion of parathyroid hormone (PTH) was evaluated by 1) adding histamine phosphate (with or without the histamine Ho receptor antagonist, cimetidine) to the medium in in vitro incubation studies with bovine parathyroid tissue, 2) infusing histamine into rats, and 3) infusing the histamine H1 receptor antagonist, diphenhydramine, or cimetidine into normal men and patients with primary hyperparathyroidism. In vitro, histamine (10-5–10-7 M) caused a dose-related significant stimulation of immunoreactive PTH (iPTH) secretion; this was blocked by the simultaneous addition of cimetidine (10-5 M). Intravenous infusion of histamine significantly increased serum iPTH in rats. In normal man, infusion of diphenhydramine had no effect, but cimetidine (300 or 450 mg) significantly decreased serum iPTH. However, cimetidine had no effect on serum iTH in primary hyperparathyroid patients. The in vitro Șbservations indicate that histamine can stimulate iPTH secretio...